Items+how to play:
shoes+4 hp pots, then you try to farm as much as you can and get the hp belt..+430 hp?..you should be lvl 6 by now..if you was mid you can try to gank lanes..and give someone else mid..so you try to get some kills and gold..so you can finish a warmog+mercury treads
you should have both items at minute 15-20
+you need minimum 100minionkills at minute 20

after that you go for whatever you need..if enemies are magic dmg dealers..you can go for a spirit visage..you should have 100 MR then..
if they are phsyical dmg dealers you can go atmas impaler+zeal
so you get your defense to 130+ vs the phsyical dmg dealers..+you get 18% crit chance of atmas..+70dmg

so you have 20% crit chance from runes+masteries+18% of atmas impaler=38%+zeal=10%=48%!
and dont forget that your dmg is 180-200 by now..+you have your E spell maxed..which gives you +100dmg too..so you have 280-350 dmg..and doing every 2nd hit a critical..thats 550-800 crits!

and you still have 3k+ hp to survive!
so you can towerdive easily + deal very much dmg

you can now go finish phantom dancer or go for bloodthirster(the sword with lifesteal) or for infinite edge or frozen mallet or guardian angel
(quicksilver shash is good against people who try to counter you by using ignite on you when you use your ult..or people who use ex. calling on you! because it removes the healreduction on you)

and one more thing i tell youUSE ELIXIERS!
the red+green ones are so good for mundo..buy them in every minute of the game
you can buy them at minute 8-9 with the belt and try ganking
you can buy them at minute 20 and use them for the first teamfights..

they give you much hp+atk dmg+crit chance+atk speed

with my build, your hp+dmg will be already very high

at lvl 18 you should have 4k hp+230 dmg(+100dmg of E spell)+70% crit chance+130 defense+100 MR
with 1 warmog+1 atmas impaler+1spirit visage+red/green elixier
you can survive most of the teamfights+deal very high dmg!

but dont forget..you arent the tank!you are just tanky
try not to be focused in teamfights..so you can deal high dmg to everyone
you will 3-4 hit a ashe/tf/etc.
she wont even deal dmg to you..you will use your ulti+ghost to get to her very fast+exhaust her and hit her 2x..she will try to run away..but since you are much faster+have cleaver to slow, she is dead 2sec later

+dont forget that when in enemy team everyone goes sunfires..you need magic resist+maybe madreds
or when in enemy team everyone is a phsyical dmg dealer..you will need a thornmail

so never use the same build every game..sometimes you need something else
but my build works for the most enemy teams..so just try it and own your enemies and get a 5.0 KDA as mundo like i did
+NEVER FORGET TO FARM AS MUNDO! HES ONE OF THE BEST FARMERS IN THIS GAME!

and whoever says warmogs is a bad item as mundo..forget that idiot..he will have a 2.0 kd as mundo..but you want a 5.0!
you need the hp for the mid/lategame to survive
+atmas impaler makes your hp=dmg

I hope I was able to help you by this guide and that i didnt forget anything..if you want to know something..just ask

on eu server 6,1 kda atm
and 2 quadras..
both were 1v4 fights..+the 5ths came after their 4 teammembers were dead..but they died too..

so it should have been pentas
so, yes this build works!

edit8:

i started using ex. calling ..and i like it
it gives some lifesteal..and it gives crit chance..which is the most important thing for this build..so its a great item..its cheap but great
and very useful against healers

edit9:
this build will only work if you are really good as mundo..but its the best build, since it works against higher elo too

or you can go for inf. edge as 4th item..it will make your dmg very high but it will take a while to finish

if you are the only tank..or really like to tank..but still want to deal some dmg..buy sunfires/force of nature instead of the ex. calling+zeal..
dont forget to buy atmas before that..and to use red+green elixier with this build..with runes/atmas impaler/elixier you will still have 50-60 % crit chance then..and ~220 dmg(with red elixier)..

So basically, you're taking the stupidity out of "Mundo is a tank," combining it with "Mundo is a DPSer" (which he is) and combining them to make him an unkillable beast, while raping everyones face?

I like it.

I play him as an exclusive DPS but I always wondered what exactly I was doing wrong. So now I'm going to have to try this build in a game. You certainly have the credibility over most people that have written guides. +1. Great guide. Could use a reformat though.

So basically, you're taking the stupidity out of "Mundo is a tank," combining it with "Mundo is a DPSer" (which he is) and combining them to make him an unkillable beast, while raping everyones face?

I like it.

I play him as an exclusive DPS but I always wondered what exactly I was doing wrong. So now I'm going to have to try this build in a game. You certainly have the credibility over most people that have written guides. +1. Great guide. Could use a reformat though.